I can't figure out how to edit my age in my profile!

I'm 21 but my profile still says I'm 20. I can't figure out how to change it because it's not listed in the regular profile settings. The only time you see someone's age or gender is when you hover your pointer over their name or avatar (it doesn't normally show up on the main profile page any more). Regardless, I still want to change it.
Any advice?